Here's why:

* Electron Configuration: Transition metals have a partially filled d orbital. They tend to lose electrons from their s and d orbitals to achieve a more stable electron configuration. This loss of electrons results in the formation of positively charged ions (cations).

* Electropositivity: Transition metals are generally electropositive, meaning they have a tendency to lose electrons and form positive ions.

* Oxidation States: Transition metals exhibit variable oxidation states, which is a direct result of their ability to lose different numbers of electrons.

Examples:

* Iron (Fe) forms Fe²⁺ and Fe³⁺ cations.

* Copper (Cu) forms Cu⁺ and Cu²⁺ cations.

* Zinc (Zn) forms Zn²⁺ cations.

Exceptions:

* Some transition metals can form anions in specific conditions. For instance, manganese (Mn) can form the MnO₄⁻ (permanganate) anion.

However, the formation of anions by transition metals is less common than the formation of cations.